Taximeter is the device that calculates the charge and has been a device with a flag that a cab driver pushes down to start the charge count. The origin is a minimum charge for hiring a taxi, to which the rate per kilometer or mile is then added. It dates back to the old mechanical taximeters, which were equipped with a flag-like lever that could be seen from outside the cab. Think tax (charge) by the meter, as in kilometer.
Flagfall or flag fall is a common Australian expression for a fixed
start fee, especially in the haulage and railroad industry. From the
Australia mobile phone industry, the expression has recently begun
to spread to other English language countries, as business jargon
for an initial fixed fee for establishing each phone call. It is
also beginning to find its way into other businesses as a synonym to